soot (n.)

Old English sot "soot," from Proto-Germanic *sotam "soot" (source also of Old Norse sot, Old Dutch soet, North Frisian sutt), literally "what settles," from PIE *sodo- (source also of Old Church Slavonic sažda, Lithuanian suodžiai, Old Irish suide, Breton huzel "soot"), suffixed form of root *sed- (1) "to sit."